Two paging modes are allowed in a CDMA system: a slotted mode and a non-slotted mode. The non-slotted mode means an operate mode in which a mobile station continuously monitors a forward-paging channel (shortened as F-PCH), rather than monitoring according to designated time slots.
Since the mobile station is required to demodulate and decode the F-PCH continuously and process messages therein, batteries will be consumed very quickly; meanwhile, system parameter messages will be broadcasted cyclically over the F-PCH when there is no paging, but for those mobile stations that have already correctly acquired these parameters and have already been in an idle state, repeated reception is also a waste.
For this reason, in order to reduce unnecessary monitoring that the mobile station performs on the F-PCH and to extend the use time of the battery in the idle state, the slotted mode, which may correspond to the non-slotted mode, has also been specified in a mobile station—base station compatibility standard for dual-mode wideband spread spectrum cellular systems (IS-95). When operating in the slotted mode, the mobile station does not monitor the F-PCH continuously in the idle state, but receives the F-PCH only in the designated time at certain time intervals according to certain rules. During each time interval when it is not necessary to receive the F-PCH, the mobile station is just like in a sleep state, a baseband processor and a radio frequency circuit reduce or even stop working so as to decrease power consumption.
In the slotted mode, a basic unit for dividing time is a time slot of the F-PCH, and its duration is 80 ms, i.e. 4 paging channel frames of a length of 20 ms respectively. In the slotted mode, the mobile station in the idle state would generally monitor the F-PCH once only at certain time intervals in the idle state, and this time interval is called a slot cycle. Within one slot cycle, the monitoring is generally performed in one or two time slots; the length of the slot cycle is a multiple of 1.28 s (=16×80 ms) and must be 1, 2, 4, 8, 16, 32, 64 or 128 times of 1.28 s; if T is used to denote the length of the slot cycle, then T=1.28×2i s, wherein i is a slot cycle index, the value of which can be an integer from 0 to 7, while the maximum value of the slot cycle may be 2048 time slots, i.e. 163.84 s. A user can adjust a desired length of the slot cycle through setting the slot cycle index of the mobile station by himself, and then reports messages such as parameter change registration, paging initiation and paging response to the system after such adjustment.
Of course, the range of the slot cycle adjusted by the user is also limited by the current network configuration conditions. There is a parameter in a system parameter message of the mobile station within the broadcast service area, i.e. a max slot cycle index, which specifies a maximum slot cycle index allowed to be used in the current system. The slot cycle index actually used by the mobile station also has to be determined according to the actual situations.
In a trunking system, in addition to the slot cycle index and other parameters of the existing system, a max push-to-talk slot cycle index (shortened as PTT Max Slot Cycle Index) is also introduced, which specifies the maximum slot cycle index and other parameters allowed to be used in the current PTT system. At the same time, in the PTT system, various reasons have resulted in problems such as slow access when the mobile station is called after power-on, so that PTT calls and other functions are restricted. However, no technical solutions that can resolve the problems have been proposed up to now.